Fundamental Skills Tutorials.
These Youtube channels are geared towards skill tutorials. The artists are from the illustration and concept art world mostly but those core skills can be used for all types of illustration.
Figure Drawing Practice
Website for practicing human anatomy if you don't have access to life drawing classes.
I have a bunch of Educational Books uploaded, you can access here: https://drive.google.com/drive/folders/0B7hYwy2PZlhvUm50Z2FhWmY4eGs